Direct esterification with first stage additive

ABSTRACT

TEREPHTHALIC ACID AND ETHYLENE GLYCOL ARE DIRECTLY ESTERIFIED IN THE PRESENCE OF AN INORGANIC METAL BORATE AND THE PRODUCT OF ESTERIFICATION IS POLYCONDENSED TO FORM A HIGH MOLECULAR WEIGHT POLYESTER.

United States Patent 3,631,153 DIRECT ESTERIFICATION WITH FIRST STAGEADDITIVE Mary E. Carter, Philadelphia, and John A. Price, Swan-thmore,Pa., assignors to FMC Corporation, Philadelphia, Pa. N0 Drawing. FiledDec. 13, 1966, Ser. No. 601,350 Int. Cl. C08g 17/013; C07c 67/00 US. Cl.260-75 R 2 Claims ABSTRACT OF THE DISCLOSURE Terephthalic acid andethylene glycol are directly esterified in the presence of an inorganicmetal borate Patented Dec. 28, 1971 is carried out in the absence of anoxygen containing gas at atmospheric or elevated pressure. The catalyticamount of borate present during the esterification reaction generallyranges from about X to about 5x10 mole per mole of terephthalic acid.

When the direct esterification stage is complete, as indicated, forexample, by the collection of clear distillate, any remaining glycol isdistilled off and a polycondensation catalyst is added to the productand condensation is continued under vacuum.

Conventional polycondensation catalysts include, for example, antimonytrioxide, antimony pentoxide, antimony trisulfide, antimony trifiuoride,antimony triphenyl, zinc acetylacetonate, lead oxide, sodium alcoholate,lithium and the product of esterification is polycondensed to form e,Zinc g ferric acetate,- g gg e ahigh molecular Weight polyestm gano-tincompoun s, organo-magnesium a 1 es, an e like. These compounds may beadded at the completion of the esterification reaction or before. Theyare generally The manufacture of polyester resin by polycondensag g g "5g F L 2 9 g ig gf tion of the product formed by the directesterification of e i i d e d s a dicarboxylic acid and a diol, is wellknown. In the case 53 f f lonbls 2 t3 53 a a T6 :5; I; e of polyethyleneterephthalate, the direct esterification proi g; a Cu t 5 g b j gx rt 2cedure has not been generally accepted for the commer- 0 mm a u 0 m a 1e m cial preparation of the polymer because of the difliculty P 3% of bcar i d out when using it, in preparing a satisfactory melt spinnable 2*b t if "W Ion may e r 6 61 r resin. The polyethylene terephthalate resinshould have %i 9 i g t f rtht d mo t t this a carboxyl content value ofbelow equivalents per mili 0 Owing e P e 18 Se 0 0 e m e lion gram-s(eq./10 gr. or rneq./kg.), a minimum b1r e- EXAMPLE fringent meltingpoint of 258 C., and an intrinsic VIS- cosity of at least 0.60. Each ofthese resin characteristic 30 A mixture containing 84 g. (0.5 mole) ofterephthalic requirements is necessary to provide a material which canacid, 62 g. (1.0 mole) of ethylene glycol, and 5 x 10 mole be meltextruded to form filaments and fibers which can of an inorganic metalborate was charged to a Fischerbe processed to form substantiallycolorless, stable, high Porter pressure assembly equipped with anitrogen sparge tenacity textile products. tube and a distilling arm.The reactor was lowered into Furthermore, from a commercial standpoint,it is desir- 35 an oil bath maintained at 260 C. and flushed for 10minable to produce polyester resin having acceptable properutes with drynitrogen. A nitrogen pressure of psi. ties in a process which takes theshortest possible time to was applied and a distillate of water-ethyleneglycol was complete. collected. When a clear liquid, i.e. solution, wasobtained,

It is an object of the present invention to prepare polythe pressure wasreduced to atmospheric and the remainethylene terephthalate resinsuitable for melt extrusion 4O ing excess glycol was distilled. The lowmolecular weight into nondegraded, processable filaments by a directesteripolymer (prepolymer) was further reacted in the presfication andpolycondensation procedure. ence of a condensation catalyst, e.g.antimony trioxide or This and other objects are accomplished inaccordance antimony trisulfide, to a high molecular weight polyesterwith this invention which concerns a method of preparunder vacuum forfour hours at 282 C. The polycondening filament-forming polyethyleneterephthalate wherein 45 sation catalyst consideration was 0.04%, basedon the terephthalic acid and ethylene glycol are directly esterifiedweight of the prepolymer. and the product of esterification ispolycondensed in the The following table sets forth conditions andresults presence of a condensation catalyst, the improvement of variousreactions carried out as described above.

TABLE Prepolymer Polyme Ester1 fi carboxyl Condencarboxy cation time,content, sation Intrinsic Melting content, Esterification additivehrs.:min. meqJkg. catalyst viscosity pt., C meq./kg

None 3:40 0. 36 261 32 None 3:40 0.80 250 40 Bismuth borate (meta) 2:050. 44 258 26 D0. 2:05 0. 99 25s 23 Cadmium borate (meta) 2:30 0. 94 26332 Calcium'borate (tetra) 2:30 1.00 258 31 Lithium borate (tetra). 2:300.92 258 22 Cobalt borate (tetra) 2:00 0.60 260 43 Manganese borate(tetra 3:00 0. 74 262 33 Lead borate (meta)* 5:40 0. 68 258 25 Nickelborate (meta)* 5:45 0. 97 258 21 *Ratio of ethylene glycol was reducedto 1.5 mole per mole of terephthalic acid.

The above table indicates that the use of the metal borates in thedirect esterification reaction consistently provides better polymersthan reactions wherein no esterification additive is used. Furthermore,in general, the use of the additive cuts esterification timeconsiderably and produces prepolymers which are more highly esterified.The higher esterification time and prepolymer carboxyl content for thelead and nickel borate additives were principally due to the reducedamount of ethylene glycol used in the reaction. The esterificationadditive provides a prepolymer which may be polycondensed to a highmolecular weight, low diethylene glycol content polymer, as indicated byits high intrinsic viscosity and melting point.

The testing used to determine the above resin charac teristics wereuniformly carried out using conventional procedures.

Various changes and modifications may be made practicing the inventionWithout departing from the spirit and scope thereof and, therefore, theinvention is not to be limited except as defined in the appended claims.

We claim:

1. A method for preparing filament-forming polyethylene terephthalateresin wherein terephthalic acid and ethylene glycol are directlyesterified and the product of esterification is condensed in thepresence of a polycondensation catalyst, the improvement comprisingcarrying out the direct esterification in the presence of a catalyticamount of bismuth borate as a catalytic direct esterification additive.

*2. A method for preparing filament-forming polyethyl- UNITED STATESPATENTS 3,007,898 11/1961 Lytton 26075 FOREIGN PATENTS 1,297,516 5/1962France 26075 WILLIAM H. SHORT, Primary Examiner,

L. P. QUAST, Assistant Examiner US. Cl. X.R.

